The present invention relates to a method and a detection system for monitoring the speed of an elevator car, wherein the movement of a drive pulley driving the elevator car and a counterweight is detected and evaluated and in the case of impermissible deviation of the speed of the elevator car from a speed preset a retardation is initiated.
A motorized cable drum is shown in U.S. Pat. No. 4,177,973, in which the motor shaft and the drum shaft are electrically monitored. A respective sensor for detection of shaft revolutions is provided for each shaft. The signals of the sensors are compared, wherein the ratio of the revolutions of the motor shaft to the revolutions of the drum shaft corresponds in the course of normal operation with the transmission ratio of the transmission. If a result departing from the transmission ratio is produced by the signal evaluation, a braking device acting on the cable drum is activated.
A disadvantage of this known equipment is that complicated hardware is necessary for monitoring the cable drum, which is costly in provision and maintenance.